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Animal Physiology 2 > The Senses > Flashcards

The Senses Flashcards

1
Q

Sensory Neurons (Afferent Neurons)

A
  • E.g. retinal cells, olfactory epithelium cells
  • Carry information from the sense organs to the brain (via an interneuron)

Stimulus acts on receptor in the neuron, causing direct depolarization
“Generator Potential” Afferent sensory neuron

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2
Q

Efferent Neurons

A
  • Spinal motor neurons, pyramidal neurons, Purkinje cells of the cerebellum.
  • Carry information from the nervous system to effector organs such as muscle - “Motor neuron”
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3
Q

Interneurons

A
  • Have short axons
  • communicate only within their immediate region
  • Communicate to other neurons
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4
Q

Multipolar neurons

A

e.g. Motor Neuron
Many cellular extensions from cell body
1 axon
Most common type in vertebrates

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5
Q

Bipolar Neurons

A

2 main processes from the cell body
1 dendrite (highly branched)
Least common type in vertebrates (but is seen in retinal cells)

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6
Q

Unipolar Neurons

A
  • Sensory neurons
  • More common in invertebrates
  • eg. environmental signals, tactile sensation
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7
Q

Ionotropic Transduction

A

A stimulus triggers channels to open by direct action.

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8
Q

Metabotropic Transduction

A

A stimulus triggers channels to open indirectly via a second messenger.

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9
Q

Epithelial Sensory Receptor Cell

A
  • Stimulus acts on receptor in receptor cell, causing depolarization and release of neurotransmitter
  • “Receptor potential”
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10
Q

Reception of Signal: Sensory Unit

A
  • Multiple sensory cells or sensory receptors within 1 cell converge onto an afferent neuron – together this is the sensory unit
  • Note different shape of sensory neuron vs motor neuron
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10
Q

Tonic Receptors

A

fire action potential as long as signal is present; slow to adapt

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11
Q

Phasic Receptors

A

do not encode duration, but may respond to beginning and end of stimulus; fast to adapt

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12
Q

Baroreceptors

A

detect pressure of vessels, the heart, digestive, reproductive and urinary tract

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13
Q

Proprioceptors

A

detect monitor position of the body

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14
Q

Tactile receptors

A

detect touch, pressure, vibrations

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15
Q

Preamble

A

Tactile receptors and accessory structures in the epidermis and dermis

  • Free nerve endings (pressure)
  • Merkel’s disks (pressure)
  • Pacinian corpuscle (vibration)
  • Ruffini corpuscle (stretch; proprioception)
  • Root hair plexus (hair displacement)
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16
Q

Vestibular sacs/Otolith organs:
Utricle (horizontal) and Saccule (vertical)

A
  • A membrane called the macula is composed of gelatinous matrix
  • Mineralized otoliths rest on the matrix
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17
Q

Semi-circular canals

A
  • No otoliths
  • Hair cells protrude into a gelatinous mass called the cupula
  • Detect angular acceleration and circular movement in all 3 planes
  • Fluid moves stereocilia toward kinocilium = activation
  • Fluid moves stereocilia away from kinocilium = inhibition
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18
Q

Hearing: The Cochlea

A

Spiral structure filled with fluids in three parallel fluid filled canals
* Cochlea is derived from the Greek word kokhlias “snail or screw”
* breaks down sound by frequency

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19
Q

Within the Scala media lies the Organ of Corti: Sensory organ of hearing

A
  • Sound transmission
  • Composed of Hair cells which rest on the Basilar membrane (blue) and the Tectorial membrane (purple)
  • Fluid in the cochlea moves with vibrations
  • Within the Scala media, this fluid vibration causes the basilar membrane to move up and down.
  • Movement of the basilar membrane causes hair cells to press against the tectorial membrane and de or hyper polarize.
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20
Q

Outer Ear: Pinna and Auditory Canal

A

Extents up to Eardrum
* Visible part is called Pinna
* Sound Collection
* Sound Transformation

21
Q

Inner Ear

A
  • Cochlea (hearing)
  • Vestibular sacs (equilibrium)
  • Semicircular canals (equilibrium)
22
Q

Ossicles - 3 Bones In The Middle Ear

A

Malleus: Receives vibrations from the eardrum
Incus: The middle ossicle
Stapes: Connected to the incus on one end and the oval window (inner / middle ear border) of the cochlea on the other.

23
Q

Structure Of A Vertebrate Hair Cell

A
  • Epithelial sensory cell’
  • contain mechanoreceptors
  • Multiple Sterocillia; actin
  • One Kinocillium
24
Q

Three Factors Help Discern Where A Touch Stimulus Is Coming From

A
  1. Receptive fields reveal location of stimulus
  2. Lateral inhibition reveals location stimulus
  3. Receptor Adaptation
25
Q

Smell and Taste: Chemoreception

A

Chemical signals
* Taste (Gustation)
* Smell (Olfaction)
* Pheromones (chemicals produced by animals)
* Some ionotropic or metabotropic

26
Q

Smell - Vertebrates

A
  • Vertebrates have 1000 genes coding for odorant receptors
  • Each odorant receptor can recognize multiple chemicals and become activated to varying degrees
  • Vertebrates can recognize upwards to 10,000 odors
27
Q

Smell - Humans

A
  • Olfactory epithelium of mammals is in the nasal cavity
  • Sensory neurons communicate to a region of the brain called the olfactory bulb
28
Q

Vomeronasal Organ

A
  • Detects pheromones (chemicals produced by animals)
  • In mammals this is on the either side of the nose near the nasal septum
29
Q

Invertebrate Sensilla

A
  • Chemo- and mechanoreceptive sensory neurons 260k sensory neurons
  • Some specialize in touch, others in chemoreception
  • Hair-like projections of cuticle
  • In the antennae – enriched in chemoreceptors
30
Q

Taste

A

Only 5 tastes: Sweet, salty, bitter, sour and umami
* Umai (delicious) mi (essence) in Japanese and corresponds to savoury or meaty sensation
* Different kinds of taste papillae contain differing numbers of taste buds

31
Q

Taste buds

A
  • Onion shaped
  • Chemicals (dissolved food) enters the pore of the taste bud – epithelial sensory cells
32
Q

Cones

A
  • Concentrated in the fovea
  • Population of about 6 million
  • Low sensitivity (not good in the dark)
  • High acuity (very good detail in the light)
  • Processes color
33
Q

Rods

A
  • Found in the periphery
  • Population of about 120 million
  • Higher sensitivity (better in the dark)
  • Good for “global information” (big objects), poor acuity (not good for details)
  • Processes black, white and shades of gray
34
Q

Lateral Inhibition In The vertebrate Retina

A
  • Horizontal cells act on bipolar cells in the outer plexiform
  • Amacrine cells in the inner plexiform
  • Inhibit neighbouring cells
35
Q

Blind Spot

A
  • Back of the retina where the optic nerve enters the eyeball
  • located in the optic disk; lacks photoreceptive cells.
36
Q

Fovea

A

Circular region in the middle of the eye that is purely photoreceptive cone cells.

37
Q

Rod signaling pathway organization to detect light/dark

A

Use the Principle of Convergence:
* Many rods synapse with a single bipolar cell
* Many bipolar cells can synapse with a single Ganglion cell
– Ganglia have a large receptive field
* E.g. 100 rods to 1 Ganglion

38
Q

Cone Signaling Pathway Detects Colour

A
  • Single cone connects to a single bipolar cells which connects to a single Ganglion cell.
  • Ganglion cells have a small receptive field, therefore a more detailed image is created from the cone cells.
39
Q

Tools For Visual Specificity

A
  1. Differential specificity of rods (dark sensitivity) and cones (colour processing).
  2. Convergence in the neural code varies sensitivity.
  3. Organization of “receptive fields” and center surround antagonism
  4. Lateral Inhibition: activity of neighbouring cells influence one another
40
Q

Compound Eyes

A
  • Composed of multicellular units called ommatidia
    – Each has its own lens
    – Creates a mosaic image
41
Q

Structure of the Ommatidium

A
  • Cornea – protective outer layer
  • Crystalline cone – lens
  • Retinular cell – photoreceptive cells; have microvilli called Rhabdom
  • Usually 8+ retinular cells in one ommatidium
42
Q

Vertebrate Eye Cells

A
  • Photoreceptors (rods and cones) within the retina (back of eye)
  • Neurons: bipolar = vertical, Amacrine and Horizontal cells = lateral
  • Ganglion Cells: Connect to the optic nerve
43
Q

Differences Between Smell And Taste

A

Smell
* Olfactory receptor cells are Bipolar sensory neuron
* G-protein coupled receptor signaling

Taste
* Gustatory receptor cells are epithelial cells
* Variety of signaling cascades (depending on taste)

44
Q

Nociceptors

A
  • Detect harmful chemicals and stimuli (sharp objects, heat) * I.e. activated by chemical, thermal or mechanical stimuli
  • Brain stimulates painful sensation
  • Evolutionarilyconserved
  • Nociceptors of the skin are free nerve endings
  • Mechanically stimulated nociceptors have high threshold (large pressure required)
45
Q

Thermoreceptors: Temperature-gated ion channels

A
  • TRPV1, is activated at temperatures greater than 42 degrees
  • Perceives pain caused by hot temperatures
  • At least three types of receptors that are activated by cold:
  • TRPA1 receptors respond to any temperature lower than 17oC – also pain from cold is perceived by this receptor
46
Q

Ciliary photoreceptors (Vertebrates)

A
  • Single cilium protruding from the cell, highly folded membrane
  • Cilium contains photopigments
  • Mammals have 2 types: Rods and Cones
  • Not neurons in the classical sense (no A.P.s)
  • Cones = colour/bright light
  • Rods = used in dim lighting, black and white shades
47
Q

Ciliary Rods and Cones

A
  • Shape differences give their names
  • Similar features:
  • Outer Segment (location of photopigments)
  • Inner Segments (nucleus) - Synaptic terminals
48
Q

Photopigments

A
  • G-protein coupled receptor, Opsin
  • Chromophore, derivative of vitamin A - Retinal is a type of chromophore
  • Chromophore absorbs light
    E.g. Rhodopsin, found in rod cells
49
Q

Phototransduction in Vertebrates

A
  • Light acts on 11-cis retinal
  • All-trans retinal dissociates from Opsin
    – Release of chromophore is called bleaching
  • Opsin (G-protein coupled receptor) is now active
  • Opsin activates Gi protein, Transducin
  • Transducin activates phosphodiesterase (PDE) consuming cGMP, making GMP
  • Reduction of 2nd messenger cGMP closes cGMP gated Na+ channel
  • cells hyper polarized

Animal Physiology 2 (17 decks)

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